G'day, I just joined the forum to maybe get some info about a Tanaka TCB 220. I bought it new years agorying to fix the original. have not used it for years but now I have moved to a country property I would like to get it up goinjg again. So far I have put new fuel in the tank, new fuel filter, spark plug and stripped the carby which is a Walbro WYJ 8 M9. I cannot find that particular carb on the Walbro site. I decided it would be just as easy to buy a new carb instead of that was a mistake, the carb I received had the throttle movement on the opposite side going in the wrong direction and it did not have the hole drilled to match the hole in the intake of the crank case. All of the replacement carbs I have seen have the primer bulb fitted on the carb where as this one has it fittled to the side of the carb. I have ordered a carb rebuild kit to maybe get the original carb back into running order. I have checked the exhaust to make sure it is clear and not gummed up, there is a good sparke at the plug. The piston has good compression. Things I have noticed so far. The original fuel pump diaphram is incorperated in the gasket where as the replacemnts look like you get a the diaphram as seperate piece. My carb has a metal plate sitting above the diaphram which I assume needs a gasket on either side of it. I must admit I am a bit puzzled by these little 2 stroke carbys, I can do a full desmo service on my Ducati Multistrata motorbike but that goes suck, squeeze, bang blow I can figure that out. I would really like to figure this out as I have a few chainsaws that require attention as well. Quick update, I just went and had a little play with it and the fuel pump diaphram is not one piece with the gasket, it was just very well stuck to is, now seperated. When pressing the primer bulb it transfers fuel through the system but the smaller return pipe has quite a few air bubbles in it. Sometimes it starts for about 2 seconds then dies.
When you press the primer bulb, if it does not fill smoothly or continues to generate bubbles, it may mean the pump is not functioning correctly or that thereβs a blockage.
Fuel Flow Issues: The presence of air bubbles in the return line is concerning and could indicate a few things:
Ensure that all fuel lines are securely connected and not cracked or damaged
It always pays to replace the fuel hoses , if the old hoses have a very small hole or crack that you can't see the carby won't work correctly.
below are a couple service manuals ,even if your carby is slightly different the operating principle is the same.
Max I have replaced the primer bulb and the rubber valve below it. All fuel lines are new and I have tried the 2 diaphrams which were in the new carby that I got. I have double checked the assembley order ie gasket plate diaphram gasket body gasket metering diaphram cover. I have not replaced the O ring where the main jet is as I don't have one as yet. Also I found that if I release the pressure on the bulb very slowly fuel moves through the system without the air bubbles coming out but when I relase it quickly the bubbles appear ? The plastic body assembley appears to have no cracks in it. I have a a repair kit K20-WYJ on order but it looks like it is the wrong kit, hopefully it has the O ring in it. I will order the correct kit WYJ-8-1 soon. Thanks for the info
Max I just checked out the Walbro site and it says the K20-WYJ is the kit required for the Tanaka TBC 220. So I will wait untill it arrives before getting the other one.
You will always have some bubbles as there is no main nozzle check valve. Now a partially clog filter screen will cause more air to be suck in via the main jet.
BTW the carb kit does contain the small o-ring for the jet.
AVB yes I took the screen out but it was good to go, no gunk in it at all. When you say some bubbles, this is producing lots of bubbles from the return line from the carb back to the primer bulb. I have wasted too much time on the carb so I will wait until the repair kit arrives and see how it goes then, thanks for your help
Well the kit came but without the O ring I wanted, renewed gaskets and diaphrams, primer bulb etc. Now no fuel coming from tank to carby, the way I see it the small fuel line that goes from the primer to the carb must create a vacuum which should then draw fuel from the tank to the carb and then the overflow of fuel then comes up to the bulb and then overflows back to the tank via the larger fuel line. This is my assumption but probably wrong. I have pulled the carb and the primer apart several times to have a look but at this stage I don't know what I am looking at. Removed the fuel screen just to eliminate that, it has the new needle and seat with new spring. Why Tanaka had to go with I remote primer I have no idea.
Nothing wrong with a remote primer they work fine, you should be able to feel a bit of suction from one of the nipples on the primer and this is the one the pick up line from the tank connects to and the it should suck fuel up, if not something is wrong with the primer
. Why Tanaka had to go with I remote primer I have no idea.
I have a Tanaka TBC 250 here Vietvet and that has to have a remote primer also, if they had a primer on the underside of the carby you couldn't get your hand to reach it because the fuel tank is under the carby and the air cleaner cover restricts access under the carby..
It's usually easier to replace the primer when it's a remote one because you don't need to remove the carby to get to the primer bulb screws.
Another way to test the primer is to connect a couple hoses and put one in a small cup of fuel and push the primer you will soon see which one is suction.
G'day Max I just went and tested the function of the primer and bulb, the smaller dia of the fuel lines picks up fuel and the larger dia fuel line to the primer returns fuel to the tank so primer is working as it should. The problem is that the smalle line goes to one side of the carby and on the other side of the carby is the fuel line from the tank. I am starting to think that there maybe a faulty check valve or something. I think I will admit defeat on this and go back to restoring my old motorbike at least I can figure them out OK.
other side of the carby is the fuel line from the tank. Other side of the carby goes back to the tank, when you push the primer you should see fuel going back into the tank
G'day Max I just went and tested the function of the primer and bulb, the smaller dia of the fuel lines picks up fuel and the larger dia fuel line to the primer returns fuel to the tank so primer is working as it should. The problem is that the smalle line goes to one side of the carby and on the other side of the carby is the fuel line from the tank. I am starting to think that there maybe a faulty check valve or something. I think I will admit defeat on this and go back to restoring my old motorbike at least I can figure them out OK.
Strange that kit came without the o-ring. My kits here has them. THe problem is if the kit don't have o-ring it going to be hard to find otherwise. But Walbro does sell a main jet kit under PN 112-706.
As fuel flow problem usually the metering diaphragm and internal filter screens causes that but the fuel filter itself can be partially clogged.
other side of the carby is the fuel line from the tank. Other side of the carby goes back to the tank, when you push the primer you should see fuel going back into the tank
Norm, the carby has 2 fuel lines, one is a 3.5mm line from the tank, the other side of the carby is a 2.5mm line which goes to the remote primer. The other side of the primer is a 3.5mm line which is the return line to the tank. I have proved that the primer is all good as it pumps fuel OK. Im am thinking that there is a check valve in the carby which seperates the pumping side of the carb to the metering side. Air is coming into the system from the metering side via the little hole in the covering plate of the metering diaphram. I have looked online to see if I can get a body assembly pump, which has thelittle pipe fitted for a remote primer or even a whole carb to replace it but they all seem to have the primer attached to the carb.
a damaged or malfunctioning diaphragm can lead to improper fuel delivery. If the diaphragm cannot maintain pressure, air can enter the fuel line.
Sticking or Malfunctioning Pump Valves: The fuel pump typically consists of inlet and outlet valves. If these valves are stuck or not sealing properly (due to dirt, wear, or damage), it can cause a disruption in fuel flow, leading to the formation of air bubbles in the fuel line.
Blockages in the Carburetor: Any debris or buildup in the carburetor can restrict fuel flow. This can create a vacuum that pulls air into the fuel line, particularly if the fuel mixture has to work harder to get through a blockage.
If the gasket between the carburetor and the engine is damaged or not sealing properly, this can allow air to leak into the fuel system, causing bubbles in the line.
Improper Carburetor Settings: If the carburetor is out of adjustment (wrong air-to-fuel mixture), it can affect fuel delivery and might lead to air being drawn into the system.
Tanaka TBC 220 fuel lines As you can see the fuel goes from the tank to the carby Thru the carby and up to the primer. It then goes from the primer back to the tank as overflow Looks like the attached file showing the whole of the machine didn't work
Last edited by Vietvet; 10/01/2501:40 PM. Reason: tried to attach image
